The invention relates to a device for the manufacture of a spun yarn from a loose fibre structure with the aid of a swirl flow. The device serves to manufacture a spun yarn from a loose fibre structure conducted to the device, whereby the fibre structure is drawn through a swirl chamber in which the fibres are subjected to a swirling flow of a fluid in order to induce rotation, and are thereby spun into a yarn.
Spinning devices of the aforementioned type are known, for example, from the publications U.S. Pat. No. 5,528,895 or U.S. Pat. No. 5,647,197 (both Murata). Such devices exhibit a fibre delivery channel and a yarn extraction channel, whereby the outlet area of the fibre delivery channel is essentially aligned against the inlet area of the yarn extraction channel and the outlet aperture of the fibre delivery channel is arranged at a distance interval from the inlet aperture of the yarn extraction channel. The swirling flow is produced in the area of this distance interval. In the area of the outlet aperture of the fibre delivery channel, in addition, twist prevention means are provided (e.g., eccentric edge, over which the fibres are drawn, or in the essentially concentric pin, about which the fibres are conducted).
The inlet area of the yarn extraction channel usually has the form of a slender spindle, which rotates as appropriate, and which, like the swirling flow, can have the function of inducing rotation. An outlet channel with an essentially ring-shaped cross-section runs around the spindle. The outlet channel leads out of the cavity, equipped as a swirl chamber, and runs essentially parallel to the yarn extraction channel. The swirl chamber in this situation has essentially the same diameter as the inlet area of the outlet channel and is equipped with nozzles directed into the chamber for blowing in a fluid (e.g. air). The fluid which is blown into the swirl chamber is conducted away through the outlet channel, whereby the swirling flow produced in the swirl chamber continues around the yarn extraction channel (spindle) into the outlet channel. The swirl chamber and an inlet area of the outlet channel accordingly essentially represent a functional unit that serves to incur the rotation.
The cross-sections of the fibre delivery channel, the yarn extraction channel, and the outlet channel are small in comparison with an average fibre length. The length of the fibre delivery channel is designed in such a way that at least a part of the fibres is still being held in the inlet area of the fibre delivery channel (e.g., by the delivery rollers of a drafting device located upstream of the fibre delivery channel) even though the forward end of which has already reached the area of the yarn extraction channel.
Fibres that are conducted to a device such as that described briefly heretofore are, on the one hand, held in the fibre structure, and so conducted from the outlet aperture of the fibre delivery channel into the yarn extraction channel essentially without rotation. On the other hand, however, in the area between the fibre delivery channel and the yarn extraction channel, the fibres are subjected to the centrifugal effect of the swirling flow, as a result of which they, or at least their end sectors, are driven radially away from the inlet aperture of the yarn extraction channel. The yarns that are manufactured by the process described then also exhibit a core of fibres or fibre sectors running essentially in the longitudinal direction of the yarn without substantial rotation, and an outer area in which the fibres or fibre sectors are rotated around the core.
This yarn structure comes about, according to a model explanation, in that the forward ends of fibres, in particular of fibres of which the following sectors are still held upstream of the fibre delivery channel, essentially pass directly into the yarn extraction channel. The following fibre sectors, however, in particular once they are no longer being held in the inlet area of the fibre delivery channel, are drawn out of the fibre structure by the swirling effect and are then rotated to form the yarn. It may also arise that forward ends of fibres are splayed outwards from the fibre structure by the swirling effect, while the following end remains in the central area of the fibre structure, which leads to the loops observed in the corresponding yarns.
In any event, fibres are bound at the same time both in the yarn being formed, as a result of which they are drawn into the yarn extraction channel, as well as being subjected to the centrifugal effect, which accelerates them centrifugally, i.e., away from the inlet aperture of the yarn extraction channel, and draws them into the extraction channel. The fibre areas drawn by the swirling flow out of the fibre structure form a fibre swirl that opens into the inlet aperture of the yarn extraction channel. The longer portions of fibre swirl wind in spiral fashion outwards around the spindle-shaped inlet area of the yarn extraction channel and are drawn in this spiral (against the force of the swirl in the extraction channel) against the inlet aperture of the yarn extraction channel. Fibres of which the forwards or following end is not drawn into the yarn being formed are, with a degree of probability that is greater with smaller fibres, sucked through the outlet channel and, as a result, represent undesirable fibre waste.
The known spinning method described is characterized in that it allows for very high spinning speeds (up to ten times higher spinning speeds than for ring spinning methods). On the other hand, it has proved to be difficult with this method to avoid a high fibre wastage and to obtain sufficient fibre rotation in the rotated outer area of the yarn to produce high yarn quality.